U.S. patent application number 16/116265 was filed with the patent office on 2019-10-03 for detection method for pixel circuit, driving method for display panel and display panel.
This patent application is currently assigned to BOE Technology Group Co., Ltd.. The applicant listed for this patent is BOE Technology Group Co., Ltd., Hefei Xinsheng Optoelectronics Technology Co., Ltd.. Invention is credited to Yongqian Li, Pan Xu, Can Yuan, Zhidong Yuan.
Application Number | 20190304362 16/116265 |
Document ID | / |
Family ID | 63133468 |
Filed Date | 2019-10-03 |
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United States Patent
Application |
20190304362 |
Kind Code |
A1 |
Yuan; Zhidong ; et
al. |
October 3, 2019 |
Detection Method for Pixel Circuit, Driving Method for Display
Panel and Display Panel
Abstract
A detection method for a pixel circuit, a driving method for a
display panel and a display panel are disclosed. The pixel circuit
includes a driving transistor including a gate electrode, and a
first terminal connected to a sensing line. The detection method
includes: applying a data voltage and a setting voltage to the
driving transistor so as to obtain a sensed voltage and obtaining a
threshold voltage of the driving transistor based on the data
voltage, the setting voltage and the sensed voltage. The data
voltage and the setting voltage are respectively applied to the
gate electrode and the first terminal so as to set the driving
transistor to be in a saturation region, the gate electrode is set
to be in a suspension state when the driving transistor is
maintained in the saturation region, and the sensed voltage is
obtained after a pre-determined time period.
Inventors: |
Yuan; Zhidong; (Beijing,
CN) ; Li; Yongqian; (Beijing, CN) ; Xu;
Pan; (Beijing, CN) ; Yuan; Can; (Beijing,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BOE Technology Group Co., Ltd.
Hefei Xinsheng Optoelectronics Technology Co., Ltd. |
Beijing
Hefei City |
|
CN
CN |
|
|
Assignee: |
BOE Technology Group Co.,
Ltd.
Beijing
CN
Hefei Xinsheng Optoelectronics Technology Co., Ltd.
Hefei City
CN
|
Family ID: |
63133468 |
Appl. No.: |
16/116265 |
Filed: |
August 29, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G09G 2310/08 20130101;
G09G 2310/0264 20130101; G09G 2320/045 20130101; G09G 3/3233
20130101; G09G 3/3266 20130101; G09G 2300/043 20130101; G09G
2320/0295 20130101; G09G 3/3291 20130101; H01L 27/3276
20130101 |
International
Class: |
G09G 3/3233 20060101
G09G003/3233; G09G 3/3266 20060101 G09G003/3266; G09G 3/3291
20060101 G09G003/3291; H01L 27/32 20060101 H01L027/32 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 27, 2018 |
CN |
201810258266.4 |
Claims
1. A detection method for a pixel circuit, the pixel circuit
comprising a driving transistor, the driving transistor comprising
a gate electrode and a first terminal, the first terminal of the
driving transistor being electrically connected to a sensing line,
the detection method comprising: applying a data voltage and a
setting voltage to the driving transistor so as to obtain a sensed
voltage, wherein the data voltage and the setting voltage are
respectively applied to the gate electrode and the first terminal
of the driving transistor so as to set the driving transistor to be
in a saturation region, the gate electrode of the driving
transistor is set to be in a suspension state when the driving
transistor is maintained in the saturation region, and the sensed
voltage is obtained through the sensing line after a pre-determined
time period; and obtaining a threshold voltage of the driving
transistor based on the data voltage, the setting voltage and the
sensed voltage.
2. The detection method for the pixel circuit according to claim 1,
wherein the data voltage and the setting voltage are applied so as
to set the driving transistor to be in a deep saturation
region.
3. The detection method for the pixel circuit according to claim 1,
wherein applying of the data voltage and the setting voltage to the
driving transistor so as to obtain the sensed voltage comprises:
performing a first detection operation, and applying a first data
voltage and a first setting voltage to the driving transistor so as
to obtain a first sensed voltage, and performing a second detection
operation, and applying a second data voltage and a second setting
voltage to the driving transistor so as to obtain a second sensed
voltage, and wherein the threshold voltage of the driving
transistor is obtained based on the first data voltage, the second
data voltage, the first setting voltage and the second setting
voltage.
4. The detection method for the pixel circuit according to claim 3,
wherein the first data voltage is not equal to the second data
voltage; and the first setting voltage is equal to the second
setting voltage.
5. The detection method for the pixel circuit according to claim 3,
wherein the first detection operation and the second detection
operation are performed continuously.
6. The detection method for the pixel circuit according to claim 3,
wherein a pre-determined time gap is provided between adjacent
display periods; and the first detection operation and the second
detection operation are performed in same one pre-determined time
gap.
7. The detection method for the pixel circuit according to claim 3,
wherein a time length of a first pre-determined time period for the
first detection operation is equal to a time length of a second
pre-determined time period for the second detection operation.
8. The detection method for the pixel circuit according to claim 7,
wherein the threshold voltage is obtained through a following
equation: Vth = Vgs 2 - Vgs 1 Vvc 2 / Vvc 1 1 - Vvc 2 / Vvc 1 ,
##EQU00006## where Vth is the threshold voltage, Vgs1 is a voltage
difference between the first data voltage and the first setting
voltage, Vgs2 is a voltage difference between the second data
voltage and the second setting voltage, Vvc1 is the first sensed
voltage, and Vvc2 is the second sensed voltage.
9. The detection method for the pixel circuit according to claim 3,
wherein the pixel circuit further comprises a first transistor and
a storage capacitor, a first terminal of the first transistor and a
second terminal of the first transistor are respectively connected
to a signal line and the gate electrode of the driving transistor,
a first terminal of the storage capacitor and a second terminal of
the storage capacitor are respectively connected to the gate
electrode of the driving transistor and the first terminal of the
driving transistor; and the detection method further comprises:
applying the data voltage to the driving transistor through turning
on the first transistor, and setting the gate electrode of the
driving transistor to be in the suspension state through turning
off the first transistor.
10. The detection method for the pixel circuit according to claim
9, wherein the pixel circuit further comprises a second transistor,
a first terminal of the second transistor is connected to the first
terminal of the driving transistor, and a second terminal of the
second transistor is connected to the sensing line; and the
detection method further comprises: applying the setting voltage to
the first terminal of the driving transistor through turning-on the
second transistor.
11. The detection method for the pixel circuit according to claim
2, wherein applying of the data voltage and the setting voltage to
the driving transistor so as to obtain the sensed voltage
comprises: performing a first detection operation, and applying a
first data voltage and a first setting voltage to the driving
transistor so as to obtain a first sensed voltage, and performing a
second detection operation, and applying a second data voltage and
a second setting voltage to the driving transistor so as to obtain
a second sensed voltage; and wherein the threshold voltage of the
driving transistor is obtained based on the first data voltage, the
second data voltage, the first setting voltage and the second
setting voltage.
12. The detection method for the pixel circuit according to claim
11, wherein the first data voltage is not equal to the second data
voltage; and the first setting voltage is equal to the second
setting voltage.
13. The detection method for the pixel circuit according to claim
12, wherein the first detection operation and the second detection
operation are performed continuously.
14. The detection method for the pixel circuit according to claim
13, wherein a pre-determined time gap is provided between adjacent
display periods; and the first detection operation and the second
detection operation are performed in same one pre-determined time
gap.
15. The detection method for the pixel circuit according to claim
14, wherein a time length of a first pre-determined time period for
the first detection operation is equal to a time length of a second
pre-determined time period for the second detection operation.
16. The detection method for the pixel circuit according to claim
4, wherein both the first setting voltage and the second setting
voltage are equal to zero.
17. The detection method for the pixel circuit according to claim
16, wherein the first data voltage is smaller than the second data
voltage.
18. A driving method for a display panel, the display panel
comprising a pixel circuit and a sensing line, the pixel circuit
comprising a driving transistor, the driving transistor comprising
a gate electrode and a first terminal, the first terminal of the
driving transistor being electrically connected to the sensing
line, the driving method comprising: performing the detection
method according to claim 1 to the pixel circuit, so as to obtain
the threshold voltage of the driving transistor of the pixel
circuit.
19. The driving method for the display panel according to claim 18,
further comprising: establishing a compensation value for the pixel
circuit according to the threshold voltage.
20. A display panel, comprising a pixel circuit, a sensing line and
a control circuit, wherein the pixel circuit comprises a driving
transistor, the driving transistor comprises a gate electrode and a
first terminal, the first terminal of the driving transistor is
electrically connected to the sensing line; and the control circuit
is configured to perform the detection method according to claim 1.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and the benefit of
Chinese Patent Application No. 201810258266.4, filed on Mar. 27,
2018, which application is incorporated herein in its entirety.
TECHNICAL FIELD
[0002] Embodiments of the present disclosure relate to a detection
method for a pixel circuit, a driving method for a display panel
and a display panel.
BACKGROUND
[0003] Organic Light Emitting Diode (OLED) display panels have
gradually attracted the attention of people due to characteristics
such as wide viewing angle, high contrast, fast response compared
with conventional display panels, and advantages such as higher
luminance, lower driving voltage and the like compared with
inorganic light emitting diode display devices. Because of the
above-mentioned characteristics, the organic light emitting diode
(OLED) display panels can be applied into mobile phones, displays,
laptops, digital cameras, instruments, and any devices with display
functions.
SUMMARY
[0004] At least one embodiment of the present disclosure provides a
detection method for a pixel circuit, the pixel circuit comprises a
driving transistor, the driving transistor comprises a gate
electrode and a first terminal, the first terminal of the driving
transistor is electrically connected to a sensing line, the
detection method comprises: applying a data voltage and a setting
voltage to the driving transistor so as to obtain a sensed voltage;
and obtaining a threshold voltage of the driving transistor based
on the data voltage, the setting voltage and the sensed voltage.
The data voltage and the setting voltage are respectively applied
to the gate electrode and the first terminal of the driving
transistor so as to set the driving transistor to be in a
saturation region, the gate electrode of the driving transistor is
set to be in a suspension state when the driving transistor is
maintained in the saturation region, and the sensed voltage is
obtained through the sensing line after a pre-determined time
period.
[0005] For example, in at least one example of the detection method
for the pixel circuit, the data voltage and the setting voltage are
applied so as to set the driving transistor to be in a deep
saturation region.
[0006] For example, in at least one example of the detection method
for the pixel circuit, applying of the data voltage and the setting
voltage to the driving transistor so as to obtain the sensed
voltage comprises: performing a first detection operation, and
applying a first data voltage and a first setting voltage to the
driving transistor so as to obtain a first sensed voltage, and
performing a second detection operation, and applying a second data
voltage and a second setting voltage to the driving transistor so
as to obtain a second sensed voltage; and the threshold voltage of
the driving transistor is obtained based on the first data voltage,
the second data voltage, the first setting voltage and the second
setting voltage.
[0007] For example, in at least one example of the detection method
for the pixel circuit, the first data voltage is not equal to the
second data voltage; and the first setting voltage is equal to the
second setting voltage.
[0008] For example, in at least one example of the detection method
for the pixel circuit, both the first setting voltage and the
second setting voltage are equal to zero.
[0009] For example, in at least one example of the detection method
for the pixel circuit, the first data voltage is smaller than the
second data voltage.
[0010] For example, in at least one example of the detection method
for the pixel circuit, the first detection operation and the second
detection operation are performed continuously.
[0011] For example, in at least one example of the detection method
for the pixel circuit, a pre-determined time gap is provided
between adjacent display periods; and the first detection operation
and the second detection operation are performed in same one
pre-determined time gap.
[0012] For example, in at least one example of the detection method
for the pixel circuit, a time length of a first pre-determined time
period for the first detection operation is equal to a second time
length of a pre-determined time period for the second detection
operation.
[0013] For example, in at least one example of the detection method
for the pixel circuit, the threshold voltage is obtained through a
following equation:
Vth = Vgs 2 - Vgs 1 Vvc 2 / Vvc 1 1 - Vvc 2 / Vvc 1 ,
##EQU00001##
[0014] where Vth is the threshold voltage, Vgs1 is a voltage
difference between the first data voltage and the first setting
voltage, Vgs2 is a voltage difference between the second data
voltage and the second setting voltage, Vvc1 is the first sensed
voltage, and Vvc2 is the second sensed voltage.
[0015] For example, in at least one example of the detection method
for the pixel circuit, the pixel circuit further comprises a first
transistor and a storage capacitor, a first terminal of the first
transistor and a second terminal of the first transistor are
respectively connected to a signal line and the gate electrode of
the driving transistor, a first terminal of the storage capacitor
and a second terminal of the storage capacitor are respectively
connected to the gate electrode of the driving transistor and the
first terminal of the driving transistor; and the detection method
further comprises: applying the data voltage to the driving
transistor through turning on the first transistor, and setting the
gate electrode of the driving transistor to be in the suspension
state through turning off the first transistor.
[0016] For example, in at least one example of the detection method
for the pixel circuit, the pixel circuit further comprises a second
transistor, a first terminal of the second transistor is connected
to the first terminal of the driving transistor, and a second
terminal of the second transistor is connected to the sensing line;
and the detection method further comprises: applying the setting
voltage to the first terminal of the driving transistor through the
second transistor.
[0017] At least one embodiment of the present disclosure further
provides a driving method for a display panel, the display panel
comprises a pixel circuit and a sensing line, the pixel circuit
comprises a driving transistor, the driving transistor comprises a
gate electrode and a first terminal, the first terminal of the
driving transistor is electrically connected to the sensing line,
the driving method comprises: performing the detection method,
provided by any one of the embodiments of the present disclosure,
to the pixel circuit, so as to obtain the threshold voltage of the
driving transistor of the pixel circuit.
[0018] For example, in at least one example of the driving method
for the display panel, the driving method further comprises:
establishing a compensation value of the pixel circuit according to
the threshold voltage.
[0019] At least one embodiment of the present disclosure further
provides a display panel, the display panel comprises a pixel
circuit, a sensing line and a control circuit, the pixel circuit
comprises a driving transistor, the driving transistor comprises a
gate electrode and a first terminal, the first terminal of the
driving transistor is electrically connected to the sensing line;
and the control circuit is configured to perform the detection
method provided by any one of the embodiments of the present
disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In order to clearly illustrate the technical solution of the
embodiments of the disclosure, the drawings of the embodiments will
be briefly described in the following; it is obvious that the
described drawings are only related to some embodiments of the
disclosure and thus are not limitative of the disclosure.
[0021] FIG. 1A is a schematic diagram of a pixel circuit;
[0022] FIG. 1B is a schematic diagram of another pixel circuit;
[0023] FIG. 1C is a schematic diagram of further another pixel
circuit;
[0024] FIG. 1D is a schematic diagram illustrating a change of a
sensed voltage over time;
[0025] FIG. 2 is an exemplary flow chart of a detection method for
a pixel circuit provided by at least one embodiment of the present
disclosure;
[0026] FIG. 3A is a schematic diagram of a pixel circuit provided
by at least one embodiment of the present disclosure;
[0027] FIG. 3B is a schematic diagram of another pixel circuit
provided by at least one embodiment of the present disclosure;
[0028] FIG. 3C is a schematic diagram of further another pixel
circuit provided by at least one embodiment of the present
disclosure;
[0029] FIG. 4 is a schematic diagram illustrating a timing diagram
of the pixel circuit as illustrated in FIG. 3A and a change of a
voltage in a sensing line over time;
[0030] FIG. 5 is a schematic diagram illustrating a simulation
result of threshold detection of a driving transistor;
[0031] FIG. 6 is a schematic diagram illustrating a comparison
result of an actual threshold value and a detected threshold value
of a driving transistor;
[0032] FIG. 7 is an exemplary flow chart of a driving method for a
display panel provided by at least one embodiment of the present
disclosure; and
[0033] FIG. 8 is a schematic diagram of a display panel provided by
at least one embodiment of the present disclosure.
DETAILED DESCRIPTION
[0034] In order to make objects, technical details and advantages
of the embodiments of the disclosure apparent, the technical
solutions of the embodiments will be described in a clearly and
fully understandable way in connection with the drawings related to
the embodiments of the disclosure. Apparently, the described
embodiments are just a part but not all of the embodiments of the
disclosure. Based on the described embodiments herein, those
skilled in the art can obtain other embodiment (s), without any
inventive work, which should be within the scope of the
disclosure.
[0035] Unless otherwise defined, all the technical and scientific
terms used herein have the same meanings as commonly understood by
one of ordinary skill in the art to which the present disclosure
belongs. The terms "first," "second," etc., which are used in the
description and the claims of the present application for
disclosure, are not intended to indicate any sequence, amount or
importance, but distinguish various components. Also, the terms
such as "a," "an," etc., are not intended to limit the amount, but
indicate the existence of at least one. The terms "comprise,"
"comprising," "include," "including," etc., are intended to specify
that the elements or the objects stated before these terms
encompass the elements or the objects and equivalents thereof
listed after these terms, but do not preclude the other elements or
objects. The phrases "connect", "connected", etc., are not intended
to define a physical connection or mechanical connection, but may
include an electrical connection, directly or indirectly. "On,"
"under," "right," "left" and the like are only used to indicate
relative position relationship, and when the position of the object
which is described is changed, the relative position relationship
may be changed accordingly.
[0036] Organic light-emitting diode (OLED) display panels generally
adopt matrix driving mode. OLED display panels can be divided into
active matrix driving mode and passive matrix driving mode
according to whether or not a switching component is introduced in
each pixel unit. AMOLED (i.e., active matrix OLED) display panels
provide a set of thin film transistors and storage capacitors in a
pixel circuit of each pixel unit, and the driving current flowing
through an OLED can be controlled through controlling the thin film
transistors and the storage capacitors, such that the OLED can emit
light according to implementation demand.
[0037] A fundamental pixel circuit adopted by AMOLED display panels
normally is a 2T1C type pixel circuit, which drives the OLED to
emit light with two thin-film transistors (TFTs) and one storage
capacitor Cst. FIG. 1A illustrates a schematic diagram of a 2T1C
type pixel circuit, and FIG. 1B illustrates a schematic diagram of
another 2T1C type pixel circuit.
[0038] As illustrated in FIG. 1A, a 2T1C type pixel circuit
includes a switching transistor T0, a driving transistor N0 and a
storage capacitor Cst. For example, a gate electrode of the
switching transistor T0 is connected to a scan line so as to
receive scan signals Scan1. For example, a source electrode of the
switching transistor T0 is connected to a data line so as to
receive data signal Vdata; and a drain electrode of the switching
transistor T0 is connected to a gate electrode of the driving
transistor N0. A source electrode of the driving transistor N0 is
connected to a first voltage terminal so as to receive a first
voltage Vdd (e.g., a high voltage), and a drain electrode of the
driving transistor N0 is connected to a positive terminal of the
OLED. A first terminal of the storage capacitor Cst is connected to
the drain electrode of the switching transistor T0 and the gate
electrode of the driving transistor N0, and a second terminal of
the storage capacitor Cst is connected to the source electrode of
the driving transistor N0 and the first voltage terminal. The
negative terminal of the OLED is connected to a second voltage
terminal so as to receive a second voltage Vss (e.g., a low
voltage, which is, for example, a grounded voltage, and smaller
than the high voltage). The 2T1C type pixel circuit adopts two TFTs
and one storage capacitor Cst to control gray scales of the display
operation of the pixel circuit. In a case that the scan signal
Scan1 is applied through the scan line to turn on the switching
transistor T0, a data driving circuit charges the storage capacitor
Cst through the switching transistor T0 by the data signal Vdata
sent over the signal line, so as to allow the data signal Vdata to
be stored into the storage capacitor Cst, and the stored data
voltages Vdata control the conducting degree of the driving
transistor N0, so as to control the value of the current, which is
flowing through the driving transistor and used for driving the
OLED to emit light, that is, the above-mentioned current determines
the gray scale of the emitted light of the pixel circuit. In the
2T1C type pixel circuit as illustrated in FIG. 1A, the switching
transistor T0 is an N type transistor and the driving transistor N0
is a P type transistor.
[0039] As illustrated in FIG. 1B, another 2T1C type pixel circuit
also includes the switching transistor T0, the driving transistor
N0 and the storage capacitor Cst, but the connections are changed
accordingly, and the driving transistor N0 is an N type transistor.
Compare to the pixel circuit as illustrated in FIG. 1A, the pixel
circuit, as illustrated in FIG. 1B, includes the following
differences: the positive terminal of the OLED is connected to the
first voltage terminal so as to receive the first voltage Vdd (the
high voltage), while the negative terminal of the OLED is connected
to the drain electrode of the driving transistor N0, the source
electrode of the driving transistor N0 is connected to the second
voltage terminal so as to receive the second voltage Vss (the low
voltage, for example, the grounded voltage). The first terminal of
the storage capacitor Cst is connected to the drain electrode of
the switching transistor T0 and the gate electrode of the driving
transistor N0, and the second terminal of the storage capacitor Cst
is connected to the source electrode of the driving transistor N0
and the second voltage terminal. The operation mechanism of the
2T1C type pixel circuit as illustrated in FIG. 1B is similar to the
operation mechanism of the 2T1C type pixel circuit as illustrated
in FIG. 1A, and no further descriptions will be given here.
[0040] Furthermore, for the pixel circuits as illustrated in FIG.
1A and FIG. 1B, the switching transistor T0 is not limited to adopt
an N type transistor, and a P type transistor can also be adopted.
In this case, the polarity (for example, high voltage level or low
voltage level) of the scan signals Scan1, which is used for turning
on or turning off the driving transistor N0, provided by a scan
control terminal can be changed accordingly.
[0041] The OLED display panels generally include a plurality of
pixel units that are arrayed (arranged in an array), and each of
the pixel units, for example, can include the above-mentioned pixel
circuit. In the OLED display panels, threshold voltages of the
driving transistors in the plurality of pixel units can be
different from each other because of the manufacturing processes.
Furthermore, because of, for example, the influence of temperature
variation or fluctuation, the threshold voltages of the driving
transistors can be shifted. Because the difference between the
threshold voltages of the driving transistors can cause display
defects (for example, display inhomogeneity), compensation of the
threshold voltage is needed.
[0042] For example, after the data signal Vdata (for example, the
data voltage) is applied to the gate electrode of the driving
transistor N0 through the switching transistor T0, the data signal
Vdata can charge the storage capacitor Cst, and the driving
transistor N0 can be turned on because of the data signal Vdata.
The voltage Vs of the source electrode or the drain electrode of
the driving transistor N0 can be changed accordingly, in which the
source electrode or the drain electrode is connected to the first
terminal of the storage capacitor Cst.
[0043] For example, FIG. 1C illustrates a pixel circuit (i.e., a
3T1C type pixel circuit) able to detect the threshold voltage of
the driving transistor, and the driving transistor N0 is an N type
transistor. For example, as illustrated in FIG. 1C, in order to
realize the compensation function, a sensing transistor S0 can be
introduced on the basis of the above-mentioned 2T1C type pixel
circuit, that is, a first terminal of the sensing transistor S0 can
be connected to the source electrode of the driving transistor N0,
a second terminal of the sensing transistor S0 is connected to the
sensing line and the detection circuit (not illustrated in
figures), such that discharge toward the detection circuit via the
sensing transistor S0 can be carried out after the driving
transistor N0 is in conduction state, so as to allow the electric
potential of the source electrode of the driving transistor N0 to
be changed. In the case that the voltage Vs of the source electrode
of the driving transistor N0 is equal to the difference between the
voltage Vg of the gate electrode of the driving transistor N0 and
the threshold voltage Vth of the driving transistor N0, the driving
transistor N0 is in cut-off state. In this case, a cut-off source
electrode voltage (i.e., the source electrode voltage Vb after the
driving transistor N0 is in cut-off state) can be obtained from the
source electrode of the driving transistor N0 via the sensing
transistor S0, which is in conduction state, after the driving
transistor N0 is in cut-off state. The threshold voltage (i.e.,
Vth=Vdata-Vb) of the driving transistor can be obtained after the
cut-off source electrode voltage of the driving transistor N0 in
cut-off state is obtained. Therefore, a compensation value of each
pixel circuit can be established (i.e., determined) based on the
threshold voltage of the driving transistor in each pixel circuit,
and compensating of the threshold voltage of each pixel circuit of
the display panel can be realized with the above-mentioned
compensation value.
[0044] For example, FIG. 1D illustrates the change of the source
electrode voltage, which is obtained from the source electrode of
the driving transistor N0 via the sensing transistor S0 in
conduction state, over time. During a detection process, the
switching transistor T0 is maintained to be in conduction state,
such that the voltage Vg of the gate electrode of the driving
transistor N0 is maintained to be Vdata. The inventors of present
disclosure note that, in the process of discharging toward the
detection circuit via the sensing line, the charging speed is
gradually decreased (i.e., the speed for increasing the sensed
voltage is decreased) along with the lapse of the time of charging
the storage capacitor Cst, after the data signal Vdata is applied
(see FIG. 1D). This is because a charging current is gradually
decreased along with an increase of the source electrode voltage
(i.e., the voltage Vs of the source electrode of the driving
transistor N0). Specifically, the current Ids outputted by the
driving transistor N0 in the saturation state can be obtained by
the follow equations:
Ids = 1 / 2 .times. K ( Vg - Vs - Vth ) 2 = 1 / 2 .times. K ( Vdata
- Vs - Vth ) 2 = 1 / 2 .times. K ( ( Vdata - Vth ) - Vs ) 2 .
##EQU00002##
where K=W/L.times.C.times..mu., W/L is the width-to-length ratio
(i.e., the ratio between the width and the length) of a channel of
the driving transistor N0, .mu. is the electron mobility, and C is
the capacitance of unit area.
[0045] During the process that the voltage Vs of the source
electrode of the driving transistor N0 is increased to Vdata-Vth,
the value of [(Vdata-Vth)-Vs] continues to decrease along with the
increase of Vs; correspondingly, the current Ids outputted by the
driving transistor N0 and the charging speed continues to decrease.
Therefore, the time Ts between the start time point of charging and
the cut-off time point of the driving transistor N0 is relatively
long.
[0046] Furthermore, the inventors further note that the difference,
which is caused by the manufacturing process, between the threshold
voltages Vth of the driving transistors of the pixel circuits in
the display panel is relatively large, in order to guarantee that
the driving transistors of the pixel circuits in the display panel
can be in conduction state, the amplitude of the data signal Vdata,
which are used for detection, is required to be relatively large;
correspondingly, the cut-off source electrode voltage Vb=Vdata-Vth
of the driving transistor N0 in cut-off state is relatively large;
in this case, the time Ts required for allowing the driving
transistor N0 to be in cut-off state is further increased,
otherwise, the measurement result is inaccurate and the
compensation effect is degraded in the case the sensed voltage is
measured before the driving transistor N0 is in cut-off state.
[0047] At least because the above-mentioned reasons, current
threshold voltage detection is normally performed during the
shutting down processes of display panels, in which the shutting
down process is a time period after the normal display process of
the display panel is finished and before the display panel is
completely shut down, and the threshold voltage detection of the
driving transistor N0 cannot be performed during the display panel
is turned on (for example, during a time period between adjacent
display periods of the display process). Therefore, real-time
monitoring and compensation cannot be realized in the display
process, and thus the compensation result and the luminance
uniformity of the display panel are decreased.
[0048] The embodiments of the present disclosure provides a
detection method for a pixel circuit, a driving method for a
display panel and a display panel, the detection method can
decrease the time required for detecting the threshold, such that
the threshold detection of the pixel circuit can be performed when
the display panel is turned on, this improves the threshold
compensation result and increases the luminance uniformity of the
display panel including the pixel circuit.
[0049] At least one embodiment of the present disclosure provides a
detection method for a pixel circuit, the pixel circuit includes a
driving transistor, the driving transistor includes a gate
electrode and a first terminal, the first terminal of the driving
transistor is electrically connected to a sensing line. The
detection method includes: applying a data voltage and a setting
voltage to the driving transistor so as to obtain a sensed voltage,
and obtaining a threshold voltage of the driving transistor based
on the data voltage, the setting voltage and the sensed voltage.
The data voltage and the setting voltage are respectively applied
to the gate electrode and the first terminal of the driving
transistor so as to set the driving transistor to be in a
saturation region; the gate electrode of the driving transistor is
set to be in a suspension state when the driving transistor is
maintained in the saturation region, and the sensed voltage is
obtained through the sensing line after a pre-determined time
period.
[0050] Non-limitive descriptions are given to the detection method
for the pixel circuit provided by the embodiments of the present
disclosure in the following with reference to a plurality of
examples. As described in the following, in case of no conflict,
different features in these specific examples can be combined so as
to obtain new examples, and the new examples are also fall within
the scope of present disclosure.
[0051] FIG. 2 illustrates a detection method for a pixel circuit
provided by an embodiment of the present disclosure, the detection
method for the pixel circuit can detect the threshold voltage Vth
of a driving transistor T3 of the pixel circuit. For example,
exemplary descriptions are given below to the detection method for
the pixel circuit provided by the embodiments of the present
disclosure with reference to the pixel circuits illustrated in FIG.
3A and FIG. 3B, but the embodiments of the present disclosure are
not limited to these cases.
[0052] For example, as illustrated in FIG. 3A, the pixel circuit
includes the driving transistor T3, and a light-emitting element EL
and a sensing line SEN, which are electrically connected to a first
terminal (or a second terminal) of the driving transistor. The
driving transistor T3 includes a gate electrode and the first
terminal, and is used for control the current flowing through the
light-emitting element EL; the sensing line SEN is electrically
connected to the first terminal of the driving transistor, a
voltage of the first terminal of the driving transistor can be set
via the sensing line SEN and a sensed voltage can be obtained via
the sensing line SEN. The pixel circuit can apply a data voltage to
the gate electrode of the driving transistor T3 and apply a setting
voltage to the first terminal (for example, a source electrode) of
the driving transistor T3, so as to control the state (for example,
in turned on or in cut-off state) of the driving transistor T3, or
control a driving current flowing through the driving transistor
T3. For example, the detection method for the pixel circuit
includes the following steps.
[0053] Step S10: applying a data voltage and a setting voltage to
the driving transistor so as to obtain a sensed voltage.
[0054] Step S20: obtaining a threshold voltage of the driving
transistor based on the data voltage, the setting voltage and the
sensed voltage.
[0055] For example, in the step S10, the data voltage (for example,
a first data voltage Vd1 or a second data voltage Vd2) and the
setting voltage (for example, a first setting voltage Vset1 or a
second setting voltage Vset2) are applied to the driving transistor
T3 so as to obtain the sensed voltage (for example, a first sensed
voltage Vvc1 or a second sensed voltage Vvc2). The above-mentioned
operation includes: applying the data voltage and the setting
voltage respectively on the gate electrode of the driving
transistor T3 and the first terminal of the driving transistor T3
so as to set the driving transistor T3 in a saturation region (for
example, in a deep saturation region); allowing the gate electrode
of the driving transistor T3 to be in a suspension state while the
driving transistor T3 is maintained at the saturation region (for
example, the deep saturation region); and obtaining the sensed
voltage via the sensing line SEN after a pre-determined time
period.
[0056] For example, as illustrated in FIG. 3A, the pixel circuit
further includes a first transistor T1 and a storage capacitor Cst.
The first transistor T1 is configured to be an input switch, and a
gate electrode, which is used as a control terminal G1, of the
first transistor T1 is connected to a scan line so as to receive
scan signals. A first terminal of the first transistor T1 is
connected to a signal line Vdat so as to receive data signals, and
the gate electrode of the driving transistor T3 is connected to a
second terminal of the first transistor T1 such that the data
signals received by the first transistor are applied to the gate
electrode of the driving transistor T3. A first terminal of the
storage capacitor Cst and a second terminal of the storage
capacitor Cst are respectively connected to the gate electrode of
the driving transistor T3 and the first terminal of the driving
transistor T3, so as to allow the storage capacitor Cst to store
the data signals.
[0057] For example, as illustrated in FIG. 3A, the pixel circuit
further includes a second transistor T2. The second transistor T2
is configured as a sensing switch, a first terminal of the second
transistor T2 is connected to the first terminal of the driving
transistor T3. A second terminal of the second transistor T2 is
connected to the sensing line SEN, so as to allow the first
terminal of the driving transistor to receive the setting voltage,
to allow a capacitor related to or formed by the sensing line to be
charged to form the sensed voltage, and to allow the sensed voltage
to be detected via the sensing line. A gate electrode, which is
used as a control terminal G2, of the second transistor T2 is
connected to a sensing scan line so as to receive a sensing control
signal. For example, according to specific implementation demands,
the pixel circuit is further connected to a first power source
terminal VDD and a second power source terminal VSS. For example,
in the case that the sensing line SEN includes parasitic
capacitance Cvc and resistance Rvc, the pixel circuit as
illustrated in FIG. 3A can be equivalent to the pixel circuit as
illustrated in FIG. 3B. The parasitic capacitance Cvc can be
charged by the current originated from the driving transistor T3,
such that the voltage corresponding to the sensing line SEN is
changed, but the embodiments of the present disclosure are not
limited to this case. In addition to use the parasitic capacitance
Cvc on the sensing line SEN, a sensing capacitor can be
additionally provided to assist to realize the detection method
provided by the embodiments of the present disclosure. A first
terminal of the sensing capacitor is connected to the sensing line
SEN, and a second terminal of the sensing capacitor is connected
to, for example, a constant voltage source (for example, the second
terminal of the sensing capacitor is grounded).
[0058] In the above-mentioned embodiment as illustrated in FIG. 3A,
the driving transistor T3 is an N type transistor, the first power
source terminal VDD is a high voltage terminal, and the second
power source terminal VSS is a low voltage terminal, in which a
voltage outputted by the low voltage terminal is smaller than a
voltage outputted by the high voltage terminal, and the low voltage
terminal is, for example, grounded. Correspondingly, the first
terminal of the driving transistor T3 is a source electrode and is
connected to the light-emitting element EL. Furthermore, the first
transistor T1 and the second transistor T2 are also N type
transistors.
[0059] In operation, for example, the data voltage provided by the
signal line Vdat is applied to the gate electrode of the driving
transistor T3 by turning on the first transistor T1 (for example,
applying a signal with a high voltage level to the control terminal
G1 of the first transistor T1); the setting voltage can be applied
to the first terminal of the driving transistor T3 by turning on
the second transistor T2 (for example, applying a signal with a
high voltage level to the control terminal G2 of the second
transistor T2). For example, the setting voltage can be provided by
a setting power source terminal Vc as illustrated in FIG. 3B, so as
to allow the gate-source voltage (difference) (Vgs) of the driving
transistor T3 is larger than the threshold voltage Vth of the
driving transistor T3 and allow the drain-source voltage (Vds, that
is, the difference between the voltage of a second terminal of a
thin film transistor and the voltage of a first terminal of the
thin film transistor) of the driving transistor T3 is larger than
the difference between the gate-source voltage and the threshold
voltage (i.e., Vds>Vgs-Vth), that is, 0<Vgs-Vth<Vds, and
therefore, the driving transistor T3 can be set in the saturation
region. For example, Vds can be in the range of 12V-36V (for
example, 24V), but the embodiments of the present disclosure are
not limited to this case.
[0060] For example, in conventional threshold voltage detection
technologies, in order to minimize the detection time of the
threshold voltage, the thin film transistor is normally set to be
in a sub-threshold region, this is because in the case that the
thin film transistor is set to be in the deep saturation region,
the thin film transistor has to change from the deep saturation
region to the sub-threshold region, and in this case, the time
required for detecting the threshold voltage is correspondingly
increased. In the case that the thin film transistor is set to be
in the sub-threshold region, the gate-source voltage Vgs and the
threshold voltage Vth of the thin film transistor satisfy the
following equation: Vgs-Vth.apprxeq.Vpr (in which Vpr can be, for
example, 2V or 3V), in this case, the voltage difference Vgs
between the voltage of the gate of the thin film transistor and the
voltage of a first terminal of the thin film transistor is slightly
larger than the threshold voltage Vth of the thin film transistor;
correspondingly, the charging current is quite small. Therefore,
compared with the conventional technologies, in which the driving
transistor T3 is set in the sub-threshold region, the embodiments
of the present disclosure set the driving transistor T3 in the
saturation region, and therefore the parasitic capacitance related
to the sensing line SEN can be charged with a larger current Ids,
such that the charge speed can be increased and the time required
for detecting the threshold can be decreased.
[0061] For an N type transistor, in the case that the transistor is
in the saturation region, the current flowing through the
transistor is increased along with the increase of the gate-source
voltage Vgs of the transistor, and the larger current is in favor
of detection. For example, in the present embodiment, according to
specific implementation demands, the driving transistor T3 can be
set in the deep saturation region. It should be noted that "the
deep saturation region" in the embodiments of the present
disclosure refers to such a region, which is closer to the liner
region in a transfer characteristic curve of the thin film
transistor, of the saturation region in the transfer characteristic
curve, in which the difference between Vgs-Vth (here Vgs is the
voltage difference between the gate electrode voltage of the thin
film transistor and the voltage of the first terminal of the thin
film transistor) is smaller than and close to the voltage
difference Vds. For example, in order to set the thin film
transistor to be in the deep saturation region, the gate-source
voltage Vgs, the drain-source voltage Vds, and the threshold
voltage Vth of the thin film transistor can satisfy the following
equation: 0<Vds-Vgs+Vth<Vpreset, and thus
Vds-Vpreset<Vgs-Vth<Vds. For example, Vds can be in the range
of 12V-36V (for example, 24V), Vpreset can be in the range of 1V-4V
(for example, 2V or 3V), but the embodiments of the present
disclosure are not limited to this case. For example, because
Vgs-Vth (for example, larger than Vds-Vpreset=22V), when the thin
film transistor in the deep saturation region, is significantly
larger than Vgs-Vth (for example, is approximately equal to
Vpr=2V), when the thin film transistor in the sub-threshold region.
Therefore, the threshold detection method provided by the
embodiments of the present disclosure can charge the capacitor with
a larger current Ids, and thus the charging speed can be further
increased and the time required for subsequent detection can be
further reduced. Because the time required for detection is
relatively short, the detection of the threshold characteristics of
the pixel circuit can be performed during the time period that the
display panel is turned on, and thus the compensation result can be
improved and the luminance uniformity of the display panel
including the pixel circuit can be increased.
[0062] For example, the gate electrode of the driving transistor T3
can be set in a suspension state by turning off the first
transistor T1 (for example, by applying a signal with a low voltage
level to the first transistor T1). Because the gate electrode of
the driving transistor T3 is in a suspension state, electric
charges stored in the storage capacitor Cst cannot be changed
suddenly through releasing or charging (i.e., the quantity of
electric charges stored in the storage capacitor Cst is remain
unchanged); correspondingly, according to the charge conservation
principle of the capacitor, the voltage difference between two
terminals of the storage capacitor Cst also remains unchanged, that
is, the voltage difference between the gate electrode of the
driving transistor T3 and the first terminal of the driving
transistor T3 is maintained as the difference between the data
voltage and the setting voltage, and therefore the voltage of the
gate electrode of the driving transistor T3 is changed along with
the source electrode voltage of the driving transistor T3.
Therefore, the driving transistor T3 is maintained at the
saturation region, and the value of the current Ids remains
unchanged. For example, the parasitic capacitor Cvc on the sensing
line SEN can be charged by the current Ids with a constant and
large value by allowing the gate electrode of the driving
transistor T3 to be in the suspension state, and therefore the
charging speed of the parasitic capacitance Cvc can be further
increased, and the time required for subsequent sensed voltage
detection can be further decreased.
[0063] For example, as illustrated in FIG. 3B, after the
pre-determined time period (for example, a pre-determined time
period T after the first transistor T1 is turned off), the sensed
voltage, which is formed by the parasitic capacitance Cvc, can be
obtained through the sensing line SEN. For example, during the
process of acquiring the sensed voltage through the sensing line
SEN, the second transistor T2 can be turned off. By turning off the
second transistor T2, further increasement of the sensed voltage in
a read phase can be prevented, and sufficient time can be reserved
for reading the sensed voltage, so as to increase the accuracy of
the sensed voltage obtained from the sensing line SEN. For example,
as illustrated in FIG. 3B, the sensing line SEN can be electrically
connected to an analog-to-digital converter ADC, so as to transform
an analog signal of the sensed voltage obtained via the sensing
line SEN into a digital signal.
[0064] For example, the threshold voltage Vth of the driving
transistor T3 can be obtained based on the data voltage, the
setting voltage and the sensed voltage. For example, the current
Ids outputted by the driving transistor T3 in the saturation region
can be obtained through the following equation:
Ids=k(Vgs-Vth).sup.2
where k=1/2.times.K=1/2.times.W/L.times.C.times..mu., W/L is the
width-to-length ratio (i.e., the ratio between the width and the
length) of a channel of the driving transistor T3, .mu. is the
electron mobility, and C is the capacitance of unit area.
[0065] For example, the time T between the turn-off time of the
first transistor T1 and the turn-off time of the second transistor
T2 (i.e., the charging time is T), the parasitic capacitance Cvc,
the sensed voltage Vvc obtained through the sensing line SEN, the
current Ids and the charging time T satisfy the following
equation:
Cvc.times.Vvc=Ids.times.T=k.times.(Vgs-Vth).sup.2.times.T
[0066] Further, the following equations can be sequentially
obtained from the above-mentioned equation:
(Vgs-Vth).sup.2=Vvc.times.Cvc/(k.times.T)=Vvc.times.u.sup.2, and
Vgs-Vth=u.times. {square root over (Vvc)}.
[0067] where u= {square root over (Cvc/(k.times.T))}. Therefore,
the voltage difference Vgs between the voltage of the gate
electrode voltage of the thin film transistor and the voltage of
the first terminal of the thin film transistor can be obtained
based on the data voltage and the setting voltage, and the
threshold voltage Vth can be obtained based on the sensed voltage
Vvc of the driving transistor T3 and the voltage difference
Vgs.
[0068] For example, during obtaining of the sensed voltage through
applying the data voltage and the setting voltage on the driving
transistor T3, a plurality of detection operations can be
preformed, for example, two detection operations can be preformed
to obtain the sensed voltage. An example that the sensed voltage is
obtained by performing two continued detection operations can
includes the following steps, and the example that the sensed
voltage is obtained by performing two detection operations is
described in the following with reference to FIG. 4-FIG. 6.
[0069] Step S101: performing a first detection operation, and
applying a first data voltage Vd1 and a first setting voltage Vset1
to the driving transistor T3 so as to obtain a first sensed voltage
Vvc1.
[0070] Step S102: performing a second detection operation, and
applying a second data voltage Vd2 and a second setting voltage
Vset2 to the driving transistor T3 so as to obtain a second sensed
voltage Vvc2; and
[0071] For example, as illustrated in FIG. 4, during a first
writing phase W1 of the first detection operation OP1, the first
transistor T1 and the second transistor T2 are turned on, such that
the first data voltage Vd1 provided by the signal line Vdat can be
applied to the gate electrode of the driving transistor T3, and the
first setting voltage Vset1 provided by the setting power source
terminal Vc can be applied to the first terminal of the driving
transistor T3, and the voltage difference Vgs between the gate
electrode of the driving transistor T3 and the first terminal of
the driving transistor T3 can be set to be equal to the difference
between the first data voltage Vd1 and the first setting voltage
Vset1. For example, the first data voltage Vd1 and the first
setting voltage Vset1 are configured to allow the driving
transistor T3 to set in, for example, the deep saturation region,
but the embodiments of the present disclosure are not limited to
this case.
[0072] For example, as illustrated in FIG. 4, after the first data
voltage Vd1 is written into the gate electrode of the driving
transistor T3 and the first setting voltage Vset1 is written into
the first terminal of the driving transistor T3, the first
transistor T1 can be turned off, such that the gate electrode of
the driving transistor T3 is set to be in the suspension state, and
the voltage difference Vgs between the gate electrode of the
driving transistor T3 and the first terminal of the driving
transistor T3 is maintained to be equal to the voltage difference
Vd1-Vset1 between the first data voltage Vd1 and the first setting
voltage Vset1, so as to keep the driving transistor T3 in the deep
saturation region.
[0073] For example, as illustrated in FIG. 4, after a first
pre-determined time period T1 (i.e., the time length of a first
charging phase C1 is T1), the second transistor T2 is turned off
and the first transistor T1 is maintained to be turned off during a
first read phase RE1 of the first detection operation OP1, such
that the first sensed voltage Vvc1 can be obtained via the sensing
line SEN.
[0074] For example, as illustrated in FIG. 4, after the first
detection operation OP1, the first transistor T1 and the second
transistor T2 are turned on during a second writing phase W2 of the
second detection operation OP2, such that the second data voltage
Vd2 provided by the signal line Vdat can be applied to the gate
electrode of the driving transistor T3, and the second setting
voltage Vset2 provided by the setting power source terminal Vc can
be applied to the first terminal of the driving transistor T3, and
the voltage difference of Vgs between the gate electrode of the
driving transistor T3 and the first terminal of the driving
transistor T3 can be set to be equal to the difference Vd2-Vset2
between the second data voltage Vd2 and the second setting voltage.
For example, the second data voltage Vd2 and the second setting
voltage Vset2 are used to allow the driving transistor T3 to be set
in, for example, the deep saturation region, but the embodiments of
the present disclosure are not limited to this case.
[0075] For example, as illustrated in FIG. 4, after the second data
voltage Vd2 is written into the gate electrode of the driving
transistor T3 and the second setting voltage Vset2 is written into
the first terminal of the driving transistor T3, the first
transistor T1 can be turned off, so as to set the gate electrode of
the driving transistor T3 to be in a suspension state, and to
maintain the voltage difference Vgs between the gate electrode of
the driving transistor T3 and the first terminal of the driving
transistor T3 to be equal to the difference Vd2-Vset2 between the
second data voltage Vd2 and the second setting voltage Vset2, such
that the driving transistor T3 can be maintained in, for example,
the deep saturation region.
[0076] For example, as illustrated in FIG. 4, after a second
pre-determined time period T2 (i.e., the time length of a second
charging phase C2 is T2), the second transistor T2 is turned off,
and the first transistor T1 is maintained to be turned off in a
second read phase RE2 of the second detection operation OP2, and
therefore, the second sensed voltage Vvc2 can be obtained through
the sensing line SEN.
[0077] For example, the equation illustrating the relationship
between the parameter u and the threshold voltage Vth at any time
can be obtained through setting the first detection operation OP1
and the second detection operation OP2, and therefore, the
threshold voltage Vth can be calculated by the equation without the
parameter u, such that the error caused by, for example, the
mobility variation can be avoided, and the accuracy of the
detection result can be further improved.
[0078] For example, as illustrated in FIG. 4, the second data
voltage Vd2 can be not equal to the first data voltage Vd1. For
example, the second data voltage Vd2 can be larger than the first
data voltage Vd1, but the embodiments of the present disclosure are
not limited to this case. For another example, according to
specific implementation demands, the second data voltage Vd2 can
also be smaller than the first data voltage Vd1. For example, as
illustrated in FIG. 4, the first setting voltage Vset1 can be equal
to the second setting voltage Vset2, such that the data calculation
amount can be reduced. For example, both the first setting voltage
Vset1 and the second setting voltage Vset2 can be equal to zero,
but the embodiments of the present disclosure are not limited to
this case. For example, in the first charging phase C1 and the
first charging phase C2, the setting power source terminal Vc can
be in a suspension state.
[0079] By performing the above-mentioned first detection operation
OP1 and second detection operation OP2, the threshold voltage Vth
of the driving transistor T3 can be obtained based on the first
data voltage Vd1, the second data voltage Vd2, the first setting
voltage Vset1 and the second setting voltage Vset2. For example,
the first data voltage Vd1, the second data voltage Vd2, the first
setting voltage Vset1, the second setting voltage Vset2, the time
length T1 of the first charging phase C1 (i.e., the length of the
pre-determined time period of the first detection operation) and
the time length T2 of the second charging phase C2 (i.e., the
length of the pre-determined time period of the second detection
operation) satisfy the following equation.
Vgs 2 - Vth Vgs 1 - Vth = u 2 u 1 .times. Vvc 2 Vvc 1 = T 2 T 1 Vvc
2 Vvc 1 = x Vvc 2 / Vvc 1 . ##EQU00003##
where x=T2/T1, and the following equations can be sequentially
obtained according to the above-mentioned equation.
Vth(1- {square root over (x)} {square root over (Vvc2/Vvc1)})=Vgs2-
{square root over (x)} {square root over
(Vvc2/Vvc1)}.times.Vgs1.
Vth = Vgs 2 - x Vvc 2 / Vvc 1 .times. Vgs 1 1 - x Vvc 2 / Vvc 1 .
##EQU00004##
[0080] For example, the time length of the first pre-determined
time period of the first detection operation and the time length of
the second pre-determined time period of the second detection
operation can be same (in this case, x=1), and the threshold
voltage of the driving transistor T3 can be obtained through the
following equation:
Vth = Vgs 1 - Vgs 2 Vvc 2 / Vvc 1 1 - Vvc 2 / Vvc 1 .
##EQU00005##
[0081] Therefore, the threshold voltage Vth of the driving
transistor T3 can be obtained based on the first data voltage Vd1,
the second data voltage Vd2, the first setting voltage Vset1 and
the second setting voltage Vset2.
[0082] For example, FIG. 5 and FIG. 6 illustrate the simulation
result of the threshold detection of the driving transistor T3 with
seven different thresholds. For example, FIG. 5 illustrates a
timing diagram of the control terminal G1 of the first transistor
T1, the control terminal G2 of the second transistor T2 and the
signal line Vdat in the first detection operation and the second
detection operation. FIG. 5 also illustrates curves Vs1, Vs2, Vs3,
Vs4, Vs5, Vs6 and Vs7 respectively illustrating the change of the
voltage of a first terminal of a driving transistor M1, a driving
transistor M2, a driving transistor M3, a driving transistor M4, a
driving transistor M5, a driving transistor M6 and a driving
transistor M7 over time. For example, FIG. 7 illustrates the
comparison between an actual threshold voltage Tr of the driving
transistor M1, the driving transistor M2, the driving transistor
M3, the driving transistor M4, the driving transistor M5, the
driving transistor M6 and the driving transistor M7 with the
threshold voltage SE obtained through the detection method provided
by the embodiments of the present disclosure. As illustrated in
FIG. 7, the threshold voltage SE obtained by the embodiments of the
present disclosure is consistent with the actual threshold voltage
Tr.
[0083] It should be noted that, the symbol "lin" in FIG. 7 means
that the coordinate axis is a linear coordinate axis, the symbol
"m" in FIG. 7 represents millivolt (for example, "120m" represents
120 millivolts), and "u" in FIG. 7 represents microsecond (for
example, "60u" represents 60 microseconds).
[0084] For example, as illustrated in FIG. 7, both the time
required for the first detection operation and the time required
for the second detection operation can be only tens of
microseconds, and therefore, the detection method for the pixel
circuit provided by the embodiments of the present disclosure can
be performed in pre-determined time gaps between adjacent display
periods.
[0085] For example, the display panel including the pixel circuit
can include a plurality of display period, and the pre-determined
time gap (time gap) can be set between adjacent display periods.
For example, each display period is used for displaying a frame of
image, and the time length of each display period is equal to the
time period between the time for displaying a first image pixel of
the frame of image and the time for displaying a last image pixel
of the frame of image. For example, a blanking time can be provided
between adjacent display periods, and the pre-determined time gap
can be at least part of the blanking time. The first detection
operation and the second detection operation can be performed in
same one pre-determined time gap, such that the error caused by,
for example, the mobility variation can be avoided, and the
accuracy of the detection result can be further improved.
[0086] For example, the first detection operation and the second
detection operation can be performed continuously, that is, the
second writing phase W2 of the second detection operation OP2 and
the first read phase RE1 of the first detection operation OP1 can
be connected with each other in time, such that the error caused
by, for example, the mobility variation can be further avoided, and
the accuracy of the detection result can be further improved.
[0087] For example, not only the detection method for the pixel
circuit provided by the embodiments of the present disclosure can
be used for detecting the threshold voltage of the driving
transistor in the pixel circuits as illustrated in FIG. 3A and FIG.
3B, but also can be used for detecting the threshold voltage of the
driving transistor in the pixel circuit as illustrated FIG. 3C.
[0088] The pixel circuit as illustrated in FIG. 3C also includes
the driving transistor T3, and the light-emitting element EL and
the sensing line SEN, which are electrically connected to the first
terminal (or the second terminal) of the driving transistors. In
the present examples, the driving transistor T3 is a P type
transistor, the first power source terminal VDD is a high voltage
terminal, the second power source terminal VSS is a low voltage
terminal, in which a voltage outputted by the low voltage terminal
is smaller than a voltage outputted by the high voltage terminal,
and the low voltage terminal is for example grounded.
Correspondingly, the first terminal of the driving transistor T3,
which is configured as a source electrode, is connected to the
light-emitting element EL. Furthermore, the first transistor T1 and
the second transistor T2 can be N type transistors, or can be P
type transistors. In order to turn on and turn off the transistor
or control the driving current flowing through the driving
transistor, corresponding control signals, data voltages or setting
voltages or the like can be chosen according to the type of the
driving transistor, and no further descriptions will be given
here.
[0089] It should be noted that, although the detection method for
the pixel circuit provided by the embodiments of the present
disclosure is described by taking the case that the pixel circuit
is a 3T1C type pixel circuit as an example, but the detection
method provided by the embodiments of the present disclosure is not
limited to be used in 3T1C type pixel circuits, for example,
according to specific implementation demands, the detection method
provided by the embodiments of the present disclosure can also be
applied to, for example, 4T1C type pixel circuits, 4T2C type pixel
circuits, 6T1C type pixel circuits, and other pixel circuits with
electrical compensation function, and no further descriptions will
be given here.
[0090] It should be noted that the transistors adopted in the
embodiments of the present disclosure can be thin film transistors
or field-effect transistors or other switching devices with similar
characteristics. A source electrode and a drain electrode of the
adopted transistor can be symmetrical in structure, and therefore,
there can be no difference in the structures of the source
electrode and the drain electrode of the transistor. In the
embodiments of present disclosure, in order to distinguish two
terminals of the transistors other than a gate electrode, which
used as a control terminal, one terminal of the two terminals is
denoted as a first terminal, and the other terminal of the two
terminals is denoted as a second terminal, and therefore, the first
terminal and the second terminal of all of or part of the
transistors in the embodiment of present disclosure can be
interchangeable when required. For example, the first terminal of
the transistor in the embodiment of present disclosure can be a
source electrode, and the second terminal of the transistor can be
a drain electrode; alternatively, the first terminal of the
transistor can be a drain electrode, and the second terminal of the
transistor can be a source electrode.
[0091] Furthermore, the transistors can be divided into N type
transistors and P type transistors according to the characteristics
of the transistors, for the sake of clarity, the exemplary
technical solution is described in detail by taking the case that
the transistors in the above-mentioned embodiments of the present
disclosure are N type transistors as an example, but the
transistors in the embodiments of the present disclosure are not
limited to adopt N type transistors, and one or more transistors of
the embodiments of the present disclosure can be implemented as P
type transistors when required, these transistors are, for example,
thin film transistors.
[0092] For example, the detection method provided by the
embodiments of the present disclosure can decrease the time
required for detecting the threshold, such that the threshold
detection of the pixel circuit can be performed during the display
panel is turned on, this improves the threshold compensation result
and increases the luminance uniformity of the display panel
including the pixel circuit.
[0093] At least one embodiment of the present disclosure further
provides a driving method for a display panel, the display panel
comprises a pixel circuit and a sensing line, the pixel circuit
comprises a driving transistor, the driving transistor comprises a
gate electrode and a first terminal, the first terminal of the
driving transistor is electrically connected to the sensing line,
the driving method comprises: performing the detection method
provided by any one of the embodiments of the present disclosure to
the pixel circuit, so as to obtain the threshold voltage of the
driving transistor of the pixel circuit.
[0094] For example, the display panel includes a plurality of the
pixel units, and each of the pixel units can include a pixel
circuit. The pixel units included by the display panel, for
example, can be arrayed, i.e., arranged in an array;
correspondingly, the pixel circuits, for example, can be arrayed.
For example, the pixel circuits included by the display panel can
be implemented as the pixel circuits as illustrated in FIG. 3A-FIG.
3C. For example, as illustrated in FIG. 7, the driving method for
the display panel provided by the present disclosure includes the
following step S310.
[0095] Step S310: performing the detection method provided by any
one of the embodiments of the present disclosure to the pixel
circuit, so as to obtain the threshold voltage of the driving
transistor of the pixel circuit.
[0096] For example, the detection method for the pixel circuit can
refer to the embodiment as illustrated in FIG. 2, and no further
descriptions will be given here. For example, according to specific
implementation demands, the driving method for the display panel
provided by the present embodiment further includes the following
step S320.
[0097] Step S320: establishing a compensation value of the pixel
circuit according to the threshold voltage.
[0098] For example, in one example, firstly, the threshold voltages
of the driving transistors of the pixel circuits can be detected
row by row; secondly, the compensation value can be established
with respect to every pixel circuit after the threshold voltages of
the driving transistors of all the pixel circuits of the display
panel are obtained; lastly, performing threshold compensation to
the display panel based on the compensation values established.
These compensation values can be stored in form of a look-up table,
which is in favor of accessing and updating.
[0099] For example, firstly, the detection method for the pixel
circuit provided by anyone of the embodiments of present disclosure
can be performed with respect to the pixel circuits in a first row,
and the threshold voltages of the driving transistors of the pixel
circuits in the first row are obtained; secondly, the detection
method for the pixel circuit provided by anyone of the embodiments
of present disclosure can be performed with respect to the pixel
circuits in a second row, and the threshold voltages of the driving
transistors of the pixel circuits in the second row are obtained;
next, the pixel circuits in other rows of the display panel can be
detected row by row until the threshold voltages of the driving
transistors of all the pixel circuits in the display panel are
obtained; lastly, the compensation value is established with
respect to every pixel circuit and the threshold compensation is
performed with respect to the display panel.
[0100] For example, in another example, according to specific
implementation demands, the threshold compensation also can be
performed by adopting the following method: after detecting and
obtaining the threshold voltages of the driving transistors of
pixel circuits in a row, establishing the compensation values with
respect to every pixel circuit in the row, and then performing
threshold compensation with respect to the pixel circuits in the
row. For example, firstly, the threshold detection, the
compensation value establishment, and the threshold compensation
can be performed with respect to the pixel circuits in a first row;
and then the threshold detection, the compensation value
establishment, and the threshold compensation can be performed with
respect to the pixel circuits in a fifth row; next, the threshold
detection, the compensation value establishment, and the threshold
compensation can be performed with respect to the pixel circuits in
a second row; . . . until the threshold detection, the compensation
value establishment, and the threshold compensation are performed
with respect to all the pixel circuits included by the display
panel, such that the threshold compensation in one display period
of the display panel is realized.
[0101] It should be noted that other steps which is indispensable
to the driving method for the display panel can refer to
conventional driving method for the display panel, this can be
understood by those skilled in the art, and no further descriptions
will be given here.
[0102] For example, the driving method for the display panel
provided by the embodiments of the present disclosure can decrease
the time required for detecting the threshold, such that the
threshold detection of the pixel circuit can be performed during
the display panel is turned on (for example, performed in the time
period located between adjacent display periods), such that
real-time compensation can be realized, and the threshold
compensation result and the luminance uniformity of the display
panel adopting the driving method can be improved.
[0103] At least one embodiment of the present disclosure further
provides a pixel circuit, a sensing line and a control circuit, in
which the pixel circuit includes a driving transistor, the driving
transistor includes a gate electrode and a first terminal, the
first terminal of the driving transistor is electrically connected
to the sensing line; and the control circuit is configured to
perform the detection method provided by any one of the embodiments
of present disclosure.
[0104] For example, FIG. 8 illustrates a schematic diagram of a
display panel provided by the embodiments of present disclosure.
For example, as illustrated in FIG. 8, the display panel includes a
pixel circuit, a sensing line and a control circuit 120. A pixel
unit in a display area of the display panel includes the pixel
circuit, and the control circuit 120 is provided at the peripheral
area outside the display area. The pixel circuit includes a driving
transistor, and the driving transistor includes a gate electrode
and a first terminal. The sensing line is electrically connected to
the first terminal of the driving transistor. For example, the
control circuit 120 is configured to perform the detection method
provided by any one of the embodiments of present disclosure. For
example, the specific implementation method of the detection method
provided by the present embodiment can refer to the embodiments as
illustrated in FIG. 2, and no further descriptions will be given
here.
[0105] For example, the display panel can further include a data
driving circuit 130, a detection circuit 140 and a scan driving
circuit (not illustrated in figures), which are also provided in
the peripheral area. For example, the control circuit 120 is
further configured to control the data driving circuit 130 and the
detection circuit 140. For example, the data driving circuit 130 is
configured to provide the first data voltage and the second data
voltage at different time according to specific implementation
demands. The scan driving circuit is configured to provide scan
signals to the first transistor and the second transistor, so as to
turn on or turn off the first transistor and the second
transistor.
[0106] For example, the pixel circuit is further configured to
receive the first data voltage and the second data voltage, and to
apply the first data voltage and the second data voltage to the
gate electrode of the driving transistor at different time. For
example, the detection circuit 140 is configured to read the first
sensed voltage and the second sensed voltage from a sensing line
SEN.
[0107] For example, the pixel circuit further includes a second
transistor T2 and alight-emitting element EL; the light-emitting
element EL, for example, can be an organic light emitting diode,
but the embodiments of the present disclosure are not limited to
this case. For example, the second terminal of the driving
transistor and the first terminal of the driving transistor can be
configured to be respectively connected to a first power source
terminal VDD and a first terminal of the light-emitting element EL,
and a second terminal of the light-emitting element EL is connected
to a second power source terminal VSS. For example, a first
terminal of the second transistor T2 is electrically connected to
the first terminal of the driving transistor, and a second terminal
of the second transistor T2 is electrically connected to the
detection circuit 140. For example, the pixel circuit further
includes the sensing line SEN, the sensing line SEN is electrically
connected to the second terminal of the above-mentioned the second
transistor T2 and the detection circuit 140.
[0108] For example, the pixel circuit further includes a first
transistor T1 and a storage capacitor Cst. The first transistor T1
is configured to obtain data signals from the data driving circuit
130 and write the data signals into the gate electrode of the
driving transistor. The storage capacitor Cst stores the data
signals. For example, the pixel circuit can also include a data
line Vdat, and a first terminal of the first transistor T1 is
connected to the data line Vdat.
[0109] For example, the control circuit 120 can also include a
processor (not illustrated in figures) and a memory, the memory
includes computer executable codes and the data required to execute
the computer executable codes, the processor executes the
executable codes so as to perform at least part of the detection
method provided by any one of the embodiments of present
disclosure.
[0110] The processor, for example, is a central processing unit
(CPU) or a processing unit in other forms having data processing
capability and/or instruction execution capability. For example,
the processor can be implemented as a general-purpose processor
(GPP) and can also be a microcontroller, a microprocessor, a
digital signal processor (DSP), a special-purpose image processing
chip, a field programmable gate array (FPGA), and the like. The
memory, for example, can include a volatile memory and/or a
non-volatile memory, for example, can include a read-only memory
(ROM), a hard disk, a flash memory, and the like. Correspondingly,
the memory can be implemented as one or more computer program
products. The computer program products can include computer
readable storage media in various forms. One or more executable
codes (for example, computer program instructions) can be stored in
the computer readable storage medium. The processor can run the
program instructions to perform the detection method provided by
any one of the embodiments of the present disclosure, so as to
obtain the threshold voltage of the driving transistor of the pixel
circuit included by the display panel, and realize the threshold
compensation function of the display panel. The memory can also
store various other application programs and various data, for
example, the threshold voltage of each pixel circuit, and various
data applied to and/or generated by the application programs.
[0111] For example, the display panel provided by the embodiments
of the present disclosure can decrease the time required for
detecting the threshold, such that the threshold detection of the
driving transistor of the pixel circuit can be performed during the
display panel is turned on (for example, performed in the time
period located between adjacent display periods), such that
real-time detection and compensation can be realized during the
display panel is turned on, and the threshold compensation result
and the luminance uniformity of the display panel can be
improved.
[0112] The following statements should be noted: [0113] (1) The
accompanying drawings involve only the structure (s) in connection
with the embodiment (s) of the present disclosure, and other
structure (s) can be referred to common design (s). [0114] (2) In
case of no conflict, features in one embodiment or in different
embodiments can be combined.
[0115] Although detailed description has been given above to the
present disclosure with general description and embodiments, it
shall be apparent to those skilled in the art that some
modifications or improvements may be made on the basis of the
embodiments of the present disclosure. Therefore, all the
modifications or improvements made without departing from the
spirit of the present disclosure shall all fall within the scope of
protection of the present disclosure.
[0116] What are described above is related to the illustrative
embodiments of the disclosure only and not limitative to the scope
of the disclosure; the scopes of the disclosure are defined by the
accompanying claims.
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